Is the Stoneweave or the boosted Vinethorn equipment better? I've not seen full sets of either to compare stats.

Example of +5 Vinethorn:



Example of +0 Stoneweave of the same kind:



So yes, the upgraded vinethorn is superior in general stats. However, stoneweave is still superior in mana and the critical, accuracy, and avoidance bonuses.

Of course upgraded stoneweave is even better though:



You don't necessarily need a full set to compare. The stat differences will be comparable with each type of equipment.

If you want to kind of have a look at VT and SW stats- sorry, don't have unupgraded equips :< - here are some of my equipped pets.
Zack has full +2 VT.
Xerxes has +4 VT relic and +2 rest of set.
Light has 3 +2 SW and 1 +4 VT
Equips are generally pretty easy to upgrade until +3 where it requires gold ore. Not sure how much this helps but I've got a variety of upgrades lol.
I personally think you should upgrade your VTs to +2 as you work towards SW - it makes grinding easier. I believe a +2 VT is on par with an unupgraded SW. StoneWeavers you don't craft yourself run upwards of 700k, so they're no small investment. It also requires a lot of materials to craft them.